56 Hillebrand — Analyses of Tysonite, Bastnasite, 



submitted by him had been pronounced by Prof. Penfield on 

 the basis of qualitative tests to be jeffersonite, a manganese- 

 zinc pyroxene, a statement supported by the analysis above 

 given, although neither the color of the mineral nor its quanti- 

 tative composition agree with the hitherto published data. In 

 Dana's Mineralogy the color is given as " greenish black, on 

 the exposed surface chocolate brown," the density as 3*36 on 

 p. 358, but 3'63 on p. 360. The discoverers of the species, 

 Keating and Yanuxem, give 3*50-3-55 for the density and 4*5 

 for the hardness. The present mineral presents all the evi- 

 dences of being fresh and unaltered, yet it is brown through- 

 out, and its analysis furnishes figures widely at variance with 

 those of Herrmann and of Pisani, but giving a better meta- 

 silicate ratio than either of their analyses. Notwithstanding 

 these discrepancies, there is no reason for ascribing to the min- 

 eral a new sub species name. The analysis is chiefly valuable 

 as showing a wide range of composition for the mineral. 



Covellite, Enargite, Stalactite. 



The only important occurrence of covellite in this country is 

 at Butte, Montana, where it occurs in splendid indigo-blue 

 masses. Specimens from the East Greyrock mine, collected 

 by Mr. Geo. W. Tower of the Geological Survey, gave almost 

 the theoretical composition as shown below. Sp. gr. at 26° C. 

 4*76, uncorrected for impurities. 



An analysis of enargite collected by Mr. Tower in theRarus 

 mine, and of a beautiful sky-blue stalactite from the Anaconda 

 mine, both at Butte, are likewise given. 



Covellite. 



Enargite. 



Stalactite. 



Cu .. 66-06 



Cu 48-67 



CuO .. 9-32 



S 33-87 



Fe -33 



FeO .. -18 



Fe.._ -14=-30FeS 2 



Zn -10 



MgO_. -08 



Insol. -11 



As 17-91 



A1 2 3 .. 10-67 





Sb.... 1-76 

 S 31-44 



SO, ... 35-05 

 PA .. 1-13 



100*18 



Ratio Cu: S as 1: 1*01 



Insol... -11 



As,0 6 . -07 

 H a O... 43-44 

 Insol... -06 





100-32 



100-00 



The stalactite was of some size, and was most readily soluble 

 in cold water, the solution giving a strong acid reaction. The 

 calculated ratio is strongly acid, showing either a mixture of 

 highly acid salts or of normal salts with free acids. 



